The present invention relates to farm implements and, more particularly, to tillage implements and like devices in which it is important to penetrate the soil at a uniform depth in all regions of the implement regardless of changes in terrain that may be encountered between the towing vehicle and the implement.
Tillage implements such as field cultivators typically have relatively large rectangular frames that have a significant front-to-rear dimension. In order to have the ground penetrating tools of the frame at the same depth in both the front and rear, it is a fairly common practice to utilize gauge wheels at the front of the main frame to assist the main transport wheels that are positioned further back toward the rear of the frame. By having both the transport and gauge wheels engaging the ground when the main frame is at its lowered, operating position, the main frame can remain substantially level as the towing tractor encounters terrain changes not yet experienced by the implement. A transverse horizontal pivot between the main frame and the tongue or hitch allows the hitch to float up and down about the transverse pivot as the tractor and main frame seek their own level conditions.
In known floating hitch arrangements, the hitch is in a floating mode at all times. When the main frame is raised into a transport position, the gauge wheels remain on the ground along with the main transport wheels. Thus, the gauge wheels remain in contact with the ground during over-the-road travel, which is not a desirable situation because the gauge wheels are typically of the castering variety and tend to wobble and gyrate back and forth at road speeds unless somehow locked in straight ahead positions. Furthermore, since the linkages that connect the gauge wheels to the main frame must be operated each time the main frame is raised and lowered, such linkages will suffer premature wear unless they are heavy duty components, which necessarily increases costs.
Yet, it is important to keep the main frame substantially level when in its transport position so that adequate ground clearance is achieved between the tools and the ground at all regions of the machine. On known equipment, unless the gauge wheels remain in contact with the ground at such time, the unsupported front end of the main frame can nose dive about the transverse flotation pivot. What is needed in the art is a way of keeping the main frame level in the transport position even though the gauge wheels are off the ground, yet allow the main frame to remain level in the field position while the hitch floats up and down as the tractor experiences changes in terrain relative to the main frame.
The present invention contemplates overcoming the deficiencies of the prior art by providing a floating hitch arrangement that can be selectively engaged and disengaged. Thus, in the field operating position, the hitch can be disposed in a floating mode in which it is free to swing up and down relative to the main frame as the gauge wheels and transport wheels maintain the main frame in a level attitude. Then, for transport, the hitch can be locked into a self-leveling mode with the main frame such that as the main frame is raised and lowered, carrying the gauge wheels therewith, the angular position of the hitch relative to the main frame is under the control of self-leveling mechanism that causes the main frame to remain level in all positions of vertical adjustment.
The self-leveling mechanism includes linkage that transmits motion of the transport wheel arms to the hitch when the self-leveling mechanism is engaged for transport. On the other hand, when the self-leveling mechanism is disengaged for field operations, there is no motion-transmitting connection between the wheel arms and the hitch such that the hitch can freely pivot up and down while the wheel arms remain in a fixed position relative to the main frame. A latch carried on the hitch can be locked and unlocked to correspondingly engage and disengage the self-leveling mechanism, and in a preferred form of the invention such latch includes a remotely actuatable hydraulic piston and cylinder assembly so that the self-leveling mechanism can be engaged and disengaged from the tractor seat. When the latch is disengaged, an upstanding lever pivoted to the hitch and forming part of the control linkage of the self-leveling mechanism is free to swing back and forth relative to the hitch as the hitch floats with terrain changes. On the other hand, when the latch is engaged, the lever is locked up and cannot swing relative to the hitch such that movement of the wheel arms to raise and lower the main frame is correspondingly transmitted to the hitch, causing invention, a strut that maintains the lever rigid to the hitch when the self-leveling mechanism is engaged has one end that can move up and down along the lever between locking and released positions. The lever has a certain amount of lost motion relative to the strut when the strut is in its released position, but when the strut is in the latched position the lever is immobilized relative to the hitch. The gauge wheels are linked mechanically to the transport wheel assemblies in such a way that, even though the transport wheels are hydraulically swung up and down relative to the main frame during adjustment of the main frame between its operating and transport positions, the gauge wheels remain at a constant position and thus are raised off the ground when the main frame is raised. On the other hand, when the gauge wheels are depth adjusted relative to the main frame, the linkage between the gauge wheels and the transport wheel assemblies responsively causes a corresponding amount of depth adjustment of the transport wheels as well.